La comida es buena = The food is good. [ it is good for something] . Like for example : The kiwi is good - El kiwi es bueno. Comer Kiwi es bueno. Eating kiwi is good.
It's like to determinate if something is good or not.
Es o no es bueno? - Is it good or not?
El pescado es bueno? - Is fish good?. Yes, It is. Si, el pescado es bueno.
Dormir es bueno? - Sleeping is good?. Yes, It is. - Si, dormir es bueno.
Another example: If you think someone is cute, lets say for example > "Kezia es bonita" , "Daniel es bonito".
When you say "esta" you are giving your opinion about the state of something at that moment.
for example, If you like the fish you are eating or seeing, you say "El pescado esta bueno" (The fish is good)
La comida esta buena. (THe food is good). Este vino esta bueno. (This wine is good).